Soil Organic Carbon Storage Research Articles

Carbon sequestration in soils and climate change mitigation-Definitions and pitfalls.

The term carbon (C) sequestration has not just become a buzzword but is something of a siren's call to scientific communicators and media outlets. Carbon sequestration is the removal of C from the atmosphere and the storage, for example, in soil. It has the potential to partially compensate for anthropogenic greenhouse gas emissions and is, therefore, an important piece in the global climate change mitigation puzzle. However, the term C sequestration is often used misleadingly and, while likely unintentional, can lead to the perpetuation of biased conclusions and exaggerated expectations about its contribution to climate change mitigation efforts. Soils have considerable potential to take up C but many are also in a state of continuous loss. In such soils, measures to build up soil C may only lead to a reduction in C losses (C loss mitigation) rather than result in real C sequestration and negative emissions. In an examination of 100 recent peer-reviewed papers on topics surrounding soil C, only 4% were found to have used the term C sequestration correctly. Furthermore, 13% of the papers equated C sequestration with C stocks. The review, further, revealed that measures leading to C sequestration will not always result in climate change mitigation when non-CO2 greenhouse gases and leakage are taken into consideration. This paper highlights potential pitfalls when using the term C sequestration incorrectly and calls for accurate usage of this term going forward. Revised and new terms are suggested to distinguish clearly between C sequestration in soils, SOC loss mitigation, negative emissions, climate change mitigation, SOC storage, and SOC accrual to avoid miscommunication among scientists and stakeholder groups in future.

Digging deeper: Assessing the predictive power of common greenhouse gas accounting tools for soil carbon sequestration under organic amendment

Effective project implementation and quantification of emissions reduction in climate-smart agriculture initiatives face challenges in measurement, monitoring, and verification. To address these challenges, predictive models are regularly used to estimate the emissions reduction potential of land management changes and to prioritize funding for projects. Despite their growing utility, few studies have evaluated the performance of publicly available model tools using site specific data. This study evaluated the performance and utility of four common model tools that represent the three Intergovernmental Panel on Climate Change model tiers to predict soil organic carbon storage and estimate greenhouse gas emissions on working lands under organic matter amendment. Field data from two long-term, compost application experiments in Washington State formed the basis for model simulations using DayCent, COMET-Farm, Cool Farm, and the Washington State Climate Smart Estimator (WaCSE). Soil carbon sequestration and emissions estimates varied among the evaluated models, which was expected given their differential data requirements and input capabilities. COMET-Farm, although easier to use, exhibited a higher level of bias compared to DayCent, which was expected as a mixed tier model. The DayCent model, the model engine for the COMET-Farm tool, demonstrated the ability to explain ∼50% more of the variation in the observed values compared to COMET-Farm when initiated using the same parameters. Cool Farm was unsuitable for estimating SOC sequestration benefits from compost application primarily because it did not add carbon to the soil pool following amendment. The differences in emissions estimates derived from WaCSE compared with other tools could be attributed solely to its highly constrained input parameters and basis in tier 1 emissions factors. We conclude that online tools can provide rapid estimates of greenhouse gas emissions reduction potential over larger areas or groups of farms but should be used with caution for site-specific estimates. Hence, it is crucial to clarify the intended purpose of an assessment and the designed function of model tools when evaluating their suitability for prioritizing funding for climate-smart agriculture initiatives at the individual farm level.

The effect of short-term plants cultivation on soil organic/inorganic carbon storage in newly formed soils

Studying total soil carbon (STC), which encompasses organic (SOC) and inorganic carbon (SIC), as well as investigating the influence of soil carbon on other soil properties, is crucial for effective global soil carbon management. This knowledge is invaluable for evaluating carbon sequestration, although its scope is currently limited. Boosting soil carbon sequestration, particularly in arid regions, has direct and indirect implications for achieving over four Sustainable Development Goals: mitigating hunger, extreme poverty, enhancing environmental preservation, and addressing global climate concerns. Research into changes within SOC and SIC across surface and subsurface soils was conducted on aeolian deposits. In this specific case study, two sites sharing similar climates and conditions were chosen as sources of wind-blown sediment parent material. The aim was to discern variations in SOC, SIC, and STC storage in surface and subsurface soils between Sistan and Baluchistan Province (with rapeseed and date orchard cultivation) and Kerman Province (with maize cultivation) in southeastern Iran. The findings highlighted an opposing pattern in SOC and storage concerning soil depth, unlike SIC. The average SOC content was higher in maize cultivation (0.2%) compared to date orchard and rapeseed cultivation (0.11%), attributed to the greater evolution of these arid soils (aridisols) in comparison to the other region (entisols). Conversely, SIC content in the three soil uses demonstrated minimal variation. The mean STC storage was greater in maize cultivation (60.35 Mg ha−1) than in date orchard (54.67 Mg ha−1) and rapeseed cultivation (53.42 Mg ha−1). Within the examined drylands, SIC, originating from aeolian deposits and soil processes, assumes a more prominent role in total carbon storage than SOC, particularly within subsurface soils. Notably, over 90% of total carbon storage exists in the form of inorganic carbon in soils.

Vegetation succession accelerated the accumulation of soil organic carbon on road-cut slopes by changing the structure of the bacterial community

More emphasis on the soil carbon sequestration of restored rock-cut slopes will be beneficial for reducing carbon emissions from the transportation sector. However, the changes in soil carbon storage with vegetation succession are unclear. We selected two different highways where the cut slopes had been restored for 3 and 10–20 years in Guangdong Province, China, as the study plots. By examining the two restored slopes at different recovery times, we analyzed the differences in soil organic carbon, soil physicochemical properties and the diversity of the soil microbial communities of road-cut slopes with vegetation succession. The soil organic carbon of restored slopes increased significantly with vegetation succession. Moreover, vegetation diversity increased soil organic carbon storage by reducing the microbial activity of Proteobacteria. Additionally, the results indicated that pH remained a key factor in controlling microbial activity and that the effect of soil moisture was site specific. Additionally, our study highlights the importance of investigating the microbial community, pH, and vegetation diversity for a more complete understanding of the mechanisms that regulate soil organic carbon dynamics in restored slope ecosystems. Understanding the multivariate processes controlling soil organic carbon dynamics should be an important goal of future soil organic carbon research for restoring ecosystems on bare slopes.

Soil Organic Carbon Dynamics and Influencing Factors in the Zoige Alpine Wetland from the 1980s to 2020 Based on a Random Forest Model

Wetlands provide important ecosystem services, such as water conservation, biodiversity protection, and carbon sequestration. The Zoige alpine wetland is the largest high-altitude swamp in the world and plays a critical role in regional ecological balance and climate change. However, little is known about the fate of its soil organic carbon (SOC) storage. In this study, we estimated the degradation status of the wetland over the past 35 years and used machine learning to investigate the dynamics and driving factors of SOC at different soil depths of the Zoige wetland in 1985, 2000, and 2020. We also simulated the future SOC balance under different scenarios. The results showed that the area of Zoige wetland has degraded by 378.71 km2 in the past 35 years. Increased precipitation and solar radiation offset the adverse effects of global warming, making the soil act as a carbon sink in the past 35 years. The total SOC storage of the wetland soils in 1985, 2000, and 2020 was estimated to be 2.03 Pg, 2.05 Pg, and 2.21 Pg, respectively, with 46.95% of SOC distributed in the subsoil layers. Climate change was the most important driving factor controlling the SOC storage of the Zoige wetland, explaining 51.33% of the SOC changes in the soil. Temperature change was always the most important factor controlling wetland SOC, and precipitation had a greater impact on the topsoil. Under the temperature control targets of 1.5 °C and 2 °C, the SOC pool of the Zoige wetland will decrease by 60.21 Tg C and 69.19 Tg C, respectively. Under scenarios of a 10% and 20% increase in precipitation, the wetland soil will accumulate an additional 46.53 Tg C and 118.89 Tg C, respectively. The study results provide important references for the sustainable management of the Zoige wetland under the background of global climate change.

Temporal and spatial effects of crop diversity on soil carbon and nitrogen storage and vertical distribution

Species-diverse plant communities can promote the accumulation of soil organic carbon (SOC) and nitrogen (SON) in both natural and semi-natural ecosystems. It is not clear however, how the accumulation and depth distribution of soil C and N might be affected in species-diverse croplands. Using a 15-year crop diversity field experiment, we ask how SOC and SON accumulation and vertical distribution (0-to-100 cm soil depth) changes in response to agricultural diversity, expressed as crop rotation (temporal effect) and intercropping (spatial effect) of staple crop species including wheat and faba bean (C3) and maize (C4). We found that rotation and intercropping across crop combinations altered the depths at which C and N were stored, over the 0–100 cm soil profile, but not the total C and N stored. There was greater SOC storage over the 0–100 cm soil profile in faba bean/maize intercropping than maize-faba bean rotation. Total SOC between 0 and 40 cm soil depth in intercropping increased by 125–164 kg C ha-1 yr-1 compared to rotation systems across crop combinations. However, rotations increased SOC at 60–80 cm in depth by 104 kg ha-1 yr-1 compared to intercropping. Also, SON stocks in rotation systems, at 60–80 cm, increased by 18 kg ha-1 yr-1 compared to intercropping systems. The accumulation and vertical distribution of SOC3 derived from roots of wheat and faba bean contributed to increase total SOC stocks and SOC vertical distribution. SOC4 derived from roots of maize did not have the same effect. Crop rotations promoted deeper root-associated SOC3 accumulation whereas intercropping promoted shallower root-associated SOC3 accumulation. Our study demonstrates how the type of crop diversification influences soil C and N sequestration via regulating root distribution, root composition and root decomposition. These findings have practical implications for soil C and N management in croplands.

Changes in aggregate-associated carbon and microbial respiration affected by aggregate size, soil depth, and altitude in a forest soil

This study investigates the variations of aggregate-associated organic carbon (OC) and microbial respiration (MR) with respect to aggregate size, soil depth, and land altitude in a forest soil. The research was conducted in Arasbaran forest, East Azerbaijan province, Iran. Four sites were selected at different altitudes: 0–600 m, 600–1200 m, 1200–1800 m, and 1800–2400 m above sea level (a.s.l.), along the north-facing slope of the forest region. Soil samples were collected at five depths: 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm, with three replications for each depth. The soil samples were then fractioned into four aggregate size classes: <0.053 mm, 0.053–0.25 mm, 0.25–2 mm, and >2 mm. Both soil samples and aggregate fractions were analyzed for OC content and MR. The results revealed that OC content and MR in both soil samples and aggregate fractions increased with altitude and decreased with soil depth. Moreover, aggregate-associated OC increased with aggregate size. Specifically, as soil aggregate sizes increased from <0.053 mm to >2 mm at different altitudes, the mean occluded OC content of aggregates increased by approximately four times. Similarly, the mean aggregate-associated MR intensified eight times with the increase in aggregate size. A significant positive correlation was also observed between OC and MR rates of all aggregates. Furthermore, aggregates larger than 2 mm exhibited the highest contribution to the total soil OC storage (47.47–57.22%) and CO2 production rate (20–21%). These findings underscore the critical role of large macro-aggregates (>2 mm) in soil carbon storage and microbial activity, particularly in surface soils at higher altitudes.

Long-term fallowing produces specific fungal taxa associated with soil carbon storage

Cropland expansion has caused the loss of soil organic carbon (SOC) and the degradation of microbial communities. Fallowing is an important strategy for soil restoration, and fungi are critical in soil fertilization. This study compared the soil properties and fungal assemblage in two adjacent environments (farmland vs. fallowing) using a 30-year field experiment composed of five treatments: fallowing or agricultural management plus no fertilization, chemical fertilization, and chemical fertilization plus cow manure or crop straw amendments. The fallowed soil had more diverse fungi and maintained a higher SOC than the artificially managed treatments. Importantly, the relative abundance of Chaetomiaceae was positively correlated with all the carbon components (SOC, dissolved organic carbon, and microbial biomass carbon) simultaneously. An RNA-Seq of Trichocladium uniseriatum, the key fungus affiliated with Chaetomiaceae, showed that straw amendment significantly upregulated the genes for T. uniseriatum melanogenesis, resulting in recalcitrant necromass formation. A remarkable CO2 assimilation capacity of T. uniseriatum was revealed by 13C-labelling assay. Therefore, T. uniseriatum improved SOC storage directly by CO2 fixation and indirectly by melanogenesis. Fertilization of agricultural systems can stimulate the growth of T. uniseriatum. T. uniseriatum inoculation promoted crop growth, facilitating C absorption from the roots. This study highlighted that the valuable microbial species resources preserved in fallowed soils can improve farmland ecosystems.

Double gains: Boosting crop productivity and reducing carbon footprints through maize-legume intercropping in the Yellow River Delta, China

The increasing demand for environmentally friendly agricultural practices has driven the need for diversified crop cultivation to optimize crop productivity while minimizing carbon footprints (CFs). However, the impacts of crop diversification on crop production and environmental benefits are still poorly understood. In this study, conducted at two sites in the Yellow River Delta, China, we investigated the effects of legume intercropping, specifically maize/soybean (M/S) and maize/peanut (M/P) systems, on crop productivity, economic return, ecosystem economic budget (NEEB), CF, and carbon sustainability index (CSI) in comparison to conventional monocrops. Crops were grown in replicated field plots and fertilized in their strips according to common practice for monocrops. Compared to the expected averages of monocrops, maize/legume intercropping demonstrated higher crop yields, with M/S achieving a 37% and 43% increase at the two sites, respectively, and M/P achieving an 11% and 20% increase. The higher overyielding in M/S was attributed to stronger selection effects, i.e., interspecific facilitation. However, the complementarity effects induced by the competitive dominance of maize were similar in both intercropping systems. Additionally, M/S exhibited greater potential for improving net revenues compared to M/P. Life cycle assessments revealed lower CFs in the intercropping systems compared to monocultures. M/S reduced CFs per unit of area by 26.8% at both sites, CFs per unit of maize equivalent energy yield by 25% and 33%, and CFs per unit of revenue by 20% and 25% at the two sites, respectively. M/P also resulted in reduced CFs, albeit to a lesser extent. Intercropping enhanced the CSI, with the highest values observed in the M/S system. However, both intercropping systems showed limited effects on soil C sequestration. Overall, our results highlight that maize/legume intercropping is a feasible approach to enhance crop productivity while reducing CFs. The M/S system outperformed the M/P system in terms of crop yields, economic benefits, and CF reduction. However, the intercropping systems showed limited effects on SOC storage. This study provides important implications for sustainable agriculture by appropriate crop diversification.

Quantifying CO2 Emissions and Carbon Sequestration from Digestate-Amended Soil Using Natural 13C Abundance as a Tracer

The untapped potential for carbon sequestration in agricultural soils represents one of the most cost-effective tools for climate change mitigation. Increasing soil organic matter also brings other agronomic benefits such as improved soil structure, enhanced water-and-nutrient-retention capacity, and biological activity. Broadly, soil organic carbon storage is achieved by increasing carbon inputs (plant residues and organic amendments) and reducing carbon outputs (soil loss mechanisms, decomposition). With a focus on carbon inputs—more specifically, organic amendments—as leverage to increase soil organic carbon, we compared the respiration rates and carbon storage of incubated soil cores amended with maize straw, manure, two digestates and the solid fraction of digestate. Using the variation in the natural 13C abundance found in C4 and C3 plants as a tracer, we were able to partition the CO2 emissions between the exogenous organic matter materials elaborated from maize (C4) and native soil organic carbon (C3). The addition of digestate resulted in an additional 65 to 77% of remaining organic carbon after 92 days. The digestate-derived CO2 was fitted to a second-order kinetic carbon model that accounts for the substrate C that is assimilated into the microbial biomass. The model predicted a carbon sequestration potential of 56 to 73% of the total applied organic carbon after one to two years. For the solid fraction, the results were higher, with 89% of the applied organic carbon after 92 days and a sequestration potential of 86%. The soil priming ranged from −19% to +136% in relation to the unamended control soil, highlighting a surprisingly wide spectrum of results that warrants the need for further research on soil–digestate interactions.

Research on soil organic carbon pool and distribution characteristics in farmland

In this paper, the researches on the estimation of cultivgated soil organic carbon storage and its variation trend were conducted in Shayang County, a typical agricultural county in Jianghan Plain in China. The results showed that the order of soil organic carbon density (SOCD) was paddy soil &gt; moisture soil &gt; yellow brown soil, and the mean values were 4.46, 3.12 and 2.55 kg/m2, respectively. No matter which soil type, the organic carbon content of soil decreased gradually from the surface to the deep soil in the form of exponential function. By analyzing and processing the organic carbon data from 2001 to 2018, the average SOCD in the topsoil increased from 3.69 to 4.25 kg/m2, with an increase of 15.18%.

Differences of SOC storage and stability between soil layers influenced by long-term fertilization in a typical paddy soil of Southern China

BackgroundThe contribution of long-term fertilization to soil organic carbon (SOC) storage has been of great concern. To assess the effects of long-term fertilization on SOC storage and stability in top and sub-soil layers, soil samples were collected from a 29-year field experimental station in a typical paddy soil in southern China. The SOC storage of whole soil and SOC fractions was quantified at three soil depths (0–20, 20–40, 40–60 cm) under four treatments: no fertilization (Control), a combination of nitrogen, phosphorus and potassium (NPK), double the rates of NPK (2NPK), NPK plus manure (NPKM).ResultsThe increase of Cinput-total was significantly higher than that of SOC storage among different treatments (p < 0.05), indicating that soil fixation of exogenous carbon is limited. Besides, the SOC accumulation and sequestration rates patterned as NPKM > 2NPK > NPK, and these rates were higher at 0–20 cm depth as compared to other depth intervals. Furthermore, for the whole profile, the SOC storage of active pool was higher in the Control (39.6 t C ha−1) than in other treatment (36.2 t C ha−1, p < 0.05). Whereas, fertilization increased the SOC storage of passive pool, ranked as NPKM > 2NPK≈NPK > Control (p < 0.05), indicating that fertilization, especially organic combined with inorganic fertilization, improved SOC stability. From the perspective of soil layers, the difference of SOC storage among treatments for passive pool was mainly resulted from the difference at surface soil, and for active pool were the deeper layers. Additionally, manure application increased the difference among soil layers.ConclusionThis study concluded that non-fertilized treatment could improve the SOC storage of active pool especially in deep soil layers, while fertilization especially manure application could improve the SOC storage and stability in surface soil and increased the difference among soil layers.Graphical

Soil organic carbon is buffered by grass inputs regardless of woody cover or fire frequency in an African savanna

Abstract Woody plant encroachment (WPE) is a global trend that occurs in many biomes, including savannas, and accelerates with fire suppression. Since WPE can result in increased storage of soil organic carbon (SOC), fire management, which may include fire suppression, can improve ecosystem carbon (C) sequestration in savannas. At our study site in Kruger National Park, South Africa, we used a long‐term (~70 year) fire experiment to study the drivers and consequences of changes in woody cover (trees and shrubs) on SOC sequestration. We surveyed four fire manipulation treatments, replicated at eight locations within the park: annual high‐intensity burns, triennial high (dry season) and low‐intensity (wet season) burns, and fire exclusion, to capture the range of fire management scenarios under consideration. The changes in woody cover were calculated over a period similar to the experiment's duration (~80 years) using aerial photographs (1944–2018). Soils were analysed to 30 cm depth for SOC and δ13C, under and away from the tree canopy to isolate local‐ and landscape‐level effects of WPE on SOC. The largest increases in woody cover occurred with fire exclusion. We found that plots with higher increases in woody cover also had higher SOC. However, trees were not the only contributor to SOC gains, sustained high inputs of C4‐derived C (grasses), even under canopies in fire suppression plots, contributed significantly to SOC. We observed little difference in SOC sequestration between cooler triennial (wet season) burns and fire suppression. Synthesis. Grass input to soil organic carbon (SOC) remained high across the full range of woody cover created by varying burning regimes. The total SOC stocks stored from tree input only matched grass‐derived SOC stocks after almost 70 years of fire exclusion. Our results point to C4 grasses as a resilient contributor to SOC under altered fire regimes and further challenge the assumption that increasing tree cover, either through afforestation schemes or fire suppression, will result in large gains in C sequestration in savanna soils, even after 70 years.

Soil organic carbon changes in China's croplands: A newly estimation based on DNDC model

Soil Organic Carbon (SOC) in cropland represents a significant facet of the terrestrial ecosystem's carbon reservoirs, playing a pivotal role in global climate change mitigation efforts. Within the specific context of China, cropland SOC not only extends its implications beyond environmental impact but also serves as a critical factor in ensuring the stability and security of the nation's food supply. However, there is an ongoing argument about the changes in SOC and their spatial and temporal distribution patterns within China's croplands. In this study, we constructed a new county-level DNDC database for 2020, building upon 2003 research that quantified SOC stock in China's cropland using the DNDC model. Our aim was to assess the SOC storage and temporal changes of China's cropland in 2020 using same methodology to enhance estimation accuracy. The simulation results of the validated DNDC model revealed that the average SOC storage of China's croplands (0–30 cm) in 2020 was 6.02 Pg C, with the Northeast region contributing 23 % (1.37 Pg C). The SOC density in China varied from 18.55 to 152.57 t C ha−1, averaging at 49.65 t C ha−1. In 2020, China's cropland transitioned from a net loss of SOC in 2003 to a carbon sink, with cropland SOC density and SOC storage increased by 18.2 % and 21.6 % respectively. Notably, despite experiencing a loss of SOC compared to 2003, the Northeast region had the highest average SOC density in China. This study highlights that despite the increase in SOC density and storage in China's croplands over the last 17 years, there remains substantial potential for carbon sequestration given the current spatial distribution of SOC density's significant heterogeneity within China. The findings of this study offer data support for China's strategy to achieve food security and carbon neutrality.

Improvement of Active Organic Carbon Distribution and Soil Quality with the Combination of Deep Tillage and No-Tillage Straw Returning Mode

During the initial period of straw return, a suitable straw return technology can lay the foundation for long-term soil fertility improvement. This study focused on the issues of backward straw return technology and blind fertilizer application in the southern part of the maize-producing area in the Northeast Plain of China. In this study, two straw return modes (2-year no-tillage straw cover + 1-year deep loosening and burying straw returning mode, NPT; 3-year rotary tillage and burying straw returning mode, RT), with RT mode as a control, were combined with different N fertilizer application rates (0, 192, 240 kg/ha). The changes in soil organic carbon (SOC) and its active components (MBC, DOC, and LOC) in the 0–40 cm soil layer were analyzed, and the carbon stratification rate, carbon pool index (CPI), SOC storages of each component, and maize yield were calculated to evaluate the short-term (3-year) differences in soil organic carbon quantity and quality in order to find suitable straw return methods and nitrogen application rate combinations. The results showed that the NPT mode increased the SOC and MBC content in the 20–30 cm soil layer, with an increase of 16.2% to 37.8% and 23.0% to 50.3%, respectively, compared with the RT mode. Under the NPT mode, the carbon pool stability was higher after nitrogen fertilizer addition, with a CPI value of 10.2% to 37.8% higher in the 20–40 cm soil layer compared with the RT mode. The differences in maize yield were not significant (p &lt; 0.05) between the nitrogen application rates of 192 kg/ha and 240 kg/ha, but the SOC storages did not show significant changes. The MBC storage had the highest value under the nitrogen application rate of 192 kg/ha. Therefore, we thought that, in the early stage of straw return, the organic carbon priming effect caused by increased microbial activity was higher under the nitrogen application rate of 192 kg/ha. Considering the aspects of not affecting maize yield and improving SOC stability, it is recommended to use the NPT mode with the application of a 240 kg/ha nitrogen fertilizer rate for straw return.

Coupling effects of soil organic carbon and moisture under different land use types, seasons and slope positions in the Loess Plateau

Understanding the response of soil organic carbon (SOC) and moisture to different land-use types, slope positions, seasonal variations, and their interactions has great significance for land use and management. However, the coupling effects of SOC and soil moisture in typical hilly and gully regions are still elusive. Therefore, in this study, five different land-use types, including cropland, abandoned land, grassland, shrubland, and forestland were selected in a typical Chinese loess hilly-gully region, and soil samples were collected from 0 to 200 cm profiles at the upper, middle, and lower slope positions in four seasons. The results demonstrated that the distributions of SOC and soil moisture were jointly significantly affected by land-use types, seasons, and slope positions (P < 0.01). Average SOC content was found to be highest in the shrubland, followed by grassland, abandoned land, forestland, and cropland. SOC storage at the lower slope position was 10.97% higher than that at the upper slope position. SOC storage in winter was 45.47% higher than that in summer. SOC storages of abandoned land, grassland, shrubland, and forestland were 17.38%, 33.08%, 52.52% and 1.26% more than that of cropland, respectively. Soil moisture fluctuated greatly in 0–100 cm layers and was stable beneath the 100 cm layers, which was highest in autumn, and lowest in summer. Whereas, under different land-use types, the soil moisture of cropland was the highest, especially significantly higher than all revegetated treatments in the 60–200 cm soil layers. Compared with cropland, soil water storage at other land-use types was averagely 36.45 % lower in the entire 200 cm soil profile. SOC was positively correlated with soil moisture under different factors. Thus, we recommend planting shrub and grass in watersheds with serious soil erosion in the semi-arid hilly and gully region, because they can sequestrate more SOC and retain more soil water.

Carbon Sequestration in Low Land Paddy Soils: Effect of Certain Cultural and Nutrient Management Practices: A Review

Carbon(C) is the only key to running in this worldly life and without carbon, nothing can be ensured, but the amount and form of C in different spheres of the earth make numerous changes. Changes in the carbon levels cause the lives of all living things. Soil carbon flux directly or indirectly affects the global climate and thus agriculture productivity. To ensuring the human rations, protection is intended for the rising populace worldwide, where the critical challenges in the agriculture sector are inevitable. Improved soil and nutrient supervisions and cultural practices are very imperative to tackling these troubles. Augmenting the productivity of various agro-ecosystems, soil productiveness, and carbon accretion via certain approaches become a must concern towards sustainable food production. “Paddy soils form the huge area of artificial swamplands on the earth, and serves as food basket for the world population also responsible for sequestering soil organic carbon potentially”. Rice accounts for around 9-10 % of the total cropland area globally, and their environmental conditions are responsible for storing organic carbon in soil, methane (CH4) production, and emit nitrous oxide (N2O) in meager amount. The present review signifies the present and future potential agricultural management practices, particularly soil and plant nutrition and their effects on soil organic carbon storage (SOCS) and carbon sequestration (CS) by paddies grown under submerged conditions compared to other crops. Increasing carbon inputs and reducing SOC losses in low land paddy soils need attention as its concern with GHGs that implies direct causes of global climate. As future direction, life-cycle assessments of certain practices in low land paddy soils helps in assessing the carbon footprints and sustaining the crop productivity consequently mitigating climate change. With this view, this review study was taken to the life of carbon in the terrestrial ecosystem and its accumulation in low land paddy soils moderated by cultural and nutrient management practices adapted for rice production in low lands.

Carbon dynamics of the plant-soil system during vegetation succession in dune-meadow cascade ecosystems in Horqin Sandy Land, China

Understanding the relationship between the plant-soil carbon dynamics and environment is important for the management of arid and semi-arid ecosystems. Under long-term overgrazing and reclamation, the landscape of the Horqin Sandy Land has transformed into a dune-meadow ecotone. However, the effects of landscape evolution on the carbon dynamics in this region remain poorly investigated. This study evaluated changes in plant-soil organic carbon content and stable carbon isotope ratios (δ13C) attributable to vegetation restoration in dune ecosystems and wetland degradation in meadow ecosystems, and evaluate the indicative implications and driving mechanisms of the 13C enrichment in the plant-soil system. The dune ecosystems comprised semimobile dune with 25- and 15-year-old Artemisia Halodendron communities (SMAH1, SMAH2), fixed dune with 30- and 40-year-old Caragana microphylla communities (FCM1, FCM2), semimobile dune with 40-year-old Salix gordejevii community (SMSG), and transitional zone with a 30-year-old artificial Populus forest (TPF) in the gentle lower part. The meadow ecosystems comprised a corn field that transformed from natural meadow over 40 years (MCF) and a natural meadow with Phragmites australis community (MPA). The results show that plant leaves in different landscapes in the cascade ecosystems had various δ13C. And the mechanism of the leaves carbon isotope fractionation with increasing leaf age was significant and consistent, but different vegetation communities had different nutrient utilization strategies during ontogeny. Landscape types and soil depths are the key factors affecting SOC content, its δ13C (δ13Cs) and SOC stock changes. And the overall soil carbon turnover was accelerated with vegetation restoration. Especially in TPF, vegetation restoration is particularly significant for SOC, which is mainly reflected in the upper 20 cm of soil profile. The degradation of MPA to MCF led to loss of SOC content and storage and accelerated the soil carbon turnover rate. The δ13Cs of the dune and meadow ecosystems were positively correlated with organic-rich litter nitrogen content and were significantly negatively correlated with SOC, soil moisture, clay content, and total organic carbon to total nitrogen ratio of organic-rich litter. The revegetation using native and introduced tree and shrub species increased SOC content in dune ecosystems and significantly promoted the degree of its coupling with soil nitrogen and water.

Assessing Soil Organic Carbon Pool for Potential Climate-Change Mitigation in Agricultural Soils—A Case Study Fayoum Depression, Egypt

It is essential to assess the soil organic carbon pool (SOCP) in dry environments to apply appropriate management techniques that address sustainable development. A significant opportunity for sustaining agricultural output and reducing climate change is the storage of soil organic carbon in agricultural soil. The goal of this study was to measure the spatial variability of SOCP content, and determine the effects of soil texture, changes in land use, and land cover on SOCP in surface soil samples. The study additionally investigated the relationships between SOCP and other characteristics, including the normalized vegetation index (NDVI) and land surface temperature (LST), as well as the effects of increasing soil organic carbon on the amount of greenhouse gases. To accomplish this goal, 45 soil surface samples were collected to a depth of 30 cm at the Fayoum depression in Egypt, and analyzed. The soil samples were representative of various soil textures and land uses. The average SOCP concentration in cultivated regions is 32.1 and in bare soils it is 6.5 Mg ha−1, with areas of 157,112.94 and 16,073.27 ha, respectively. According to variances in soil textures, sandy soils have the lowest SOCP (1.8 Mg ha−1) and clay loam soils have the highest concentrations (49 Mg ha−1). Additionally, fruit-growing regions have the greatest SOCP values and may therefore be better suited for carbon sequestration. The overall average SOCP showed 32.12 Mg C ha−1 for cultivated areas. A rise in arable land was accompanied by a 112,870.09 Mg C rise in SOCP. With an increase in soil organic carbon, stored carbon dioxide emissions (greenhouse gases) would be reduced by 414,233.24 Mg CO2. We should consider improving fertilization, irrigation methods, the use of the multiple cropping index, decreasing desertion rates, appropriate crop rotation, and crop variety selection. The research highlights the significance of expanding cultivated areas towards sustainable carbon sequestration and the climate-change-mitigation potential.

High resolution mapping shows differences in soil carbon and nitrogen stocks in areas of varying landscape history in Canadian lowland tundra

Soil organic carbon (SOC) in Arctic coastal polygonal tundra is vulnerable to climate change, especially in soils with occurrence of large amounts of ground ice. Pan-arctic studies of mapping SOC exist, yet they fail to describe the high spatial variability of SOC storage in permafrost landscapes. An important factor is the landscape history which determines landform development and consequently the spatial variability of SOC. Our aim was to map SOC stocks, and which environmental variables that determine SOC, in two adjacent coastal areas along Canadian Beaufort Sea coast with different glacial history. We used the machine learning technique random forest and environmental variables to map the spatial distribution of SOC stocks down to 1 m depth at a spatial resolution of 2 m for depth increments of 0–5, 5–15, 15–30, 30–60 and 60–100 cm.The results show that the two study areas had large differences in SOC stocks in the depth 60–100 cm due to high amounts of ground ice in one of the study areas. There are also differences in variable importance of the explanatory variables between the two areas. The area low in ground ice content had with 66.6 kg C/m−2 more stored SOC than the area rich in ground ice content with 40.0 kg C/m−2. However, this SOC stock could be potentially more vulnerable to climate change if ground ice melts and the ground subsides. The average N stock of the area low in ground ice is 3.77 kg m−2 and of the area rich in ground ice is 3.83 kg m−2.These findings support that there is a strong correlation between ground ice and SOC, with less SOC in ice-rich layers on a small scale. In addition to small scale studies of SOC mapping, detailed maps of ground ice content and distribution are needed for a validation of large-scale quantifications of SOC stocks and transferability of models.